1--- 2c: Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3SPDX-License-Identifier: curl 4Title: curl_printf 5Section: 3 6Source: libcurl 7See-also: 8 - fprintf (3) 9 - printf (3) 10 - sprintf (3) 11 - vprintf (3) 12Protocol: 13 - All 14--- 15 16# NAME 17 18curl_maprintf, curl_mfprintf, curl_mprintf, curl_msnprintf, curl_msprintf 19curl_mvaprintf, curl_mvfprintf, curl_mvprintf, curl_mvsnprintf, 20curl_mvsprintf - formatted output conversion 21 22# SYNOPSIS 23 24~~~c 25#include <curl/mprintf.h> 26 27int curl_mprintf(const char *format, ...); 28int curl_mfprintf(FILE *fd, const char *format, ...); 29int curl_msprintf(char *buffer, const char *format, ...); 30int curl_msnprintf(char *buffer, size_t maxlength, const char *format, ...); 31int curl_mvprintf(const char *format, va_list args); 32int curl_mvfprintf(FILE *fd, const char *format, va_list args); 33int curl_mvsprintf(char *buffer, const char *format, va_list args); 34int curl_mvsnprintf(char *buffer, size_t maxlength, const char *format, 35 va_list args); 36char *curl_maprintf(const char *format , ...); 37char *curl_mvaprintf(const char *format, va_list args); 38~~~ 39 40# DESCRIPTION 41 42These functions produce output according to the format string and given 43arguments. They are mostly clones of the well-known C-style functions but 44there are slight differences in behavior. 45 46We discourage users from using any of these functions in new applications. 47 48Functions in the curl_mprintf() family produce output according to a format as 49described below. The functions **curl_mprintf()** and **curl_mvprintf()** 50write output to stdout, the standard output stream; **curl_mfprintf()** and 51**curl_mvfprintf()** write output to the given output stream; 52**curl_msprintf()**, **curl_msnprintf()**, **curl_mvsprintf()**, and 53**curl_mvsnprintf()** write to the character string **buffer**. 54 55The functions **curl_msnprintf()** and **curl_mvsnprintf()** write at most 56*maxlength* bytes (including the terminating null byte ('0')) to 57*buffer*. 58 59The functions **curl_mvprintf()**, **curl_mvfprintf()**, 60**curl_mvsprintf()**, **curl_mvsnprintf()** are equivalent to the 61functions **curl_mprintf()**, **curl_mfprintf()**, **curl_msprintf()**, 62**curl_msnprintf()**, respectively, except that they are called with a 63*va_list* instead of a variable number of arguments. These functions do 64not call the *va_end* macro. Because they invoke the *va_arg* macro, 65the value of *ap* is undefined after the call. 66 67The functions **curl_maprintf()** and **curl_mvaprintf()** return the 68output string as pointer to a newly allocated memory area. The returned string 69must be curl_free(3)ed by the receiver. 70 71All of these functions write the output under the control of a format string 72that specifies how subsequent arguments are converted for output. 73 74# FORMAT STRING 75 76The format string is composed of zero or more directives: ordinary characters 77(not %), which are copied unchanged to the output stream; and conversion 78specifications, each of which results in fetching zero or more subsequent 79arguments. Each conversion specification is introduced by the character %, and 80ends with a conversion specifier. In between there may be (in this order) zero 81or more *flags*, an optional minimum *field width*, an optional 82*precision* and an optional *length modifier*. 83 84# The $ modifier 85 86The arguments must correspond properly with the conversion specifier. By 87default, the arguments are used in the order given, where each '*' (see Field 88width and Precision below) and each conversion specifier asks for the next 89argument (and it is an error if insufficiently many arguments are given). One 90can also specify explicitly which argument is taken, at each place where an 91argument is required, by writing "%m$" instead of '%' and "*m$" instead 92of '*', where the decimal integer m denotes the position in the argument list 93of the desired argument, indexed starting from 1. Thus, 94~~~c 95 curl_mprintf("%*d", width, num); 96~~~ 97and 98~~~c 99 curl_mprintf("%2$*1$d", width, num); 100~~~ 101are equivalent. The second style allows repeated references to the same 102argument. 103 104If the style using '$' is used, it must be used throughout for all conversions 105taking an argument and all width and precision arguments, but it may be mixed 106with "%%" formats, which do not consume an argument. There may be no gaps in 107the numbers of arguments specified using '$'; for example, if arguments 1 and 1083 are specified, argument 2 must also be specified somewhere in the format 109string. 110 111# Flag characters 112 113The character % is followed by zero or more of the following flags: 114 115## # 116 117The value should be converted to its "alternate form". 118 119## 0 120 121The value should be zero padded. 122 123## - 124 125The converted value is to be left adjusted on the field boundary. (The default 126is right justification.) The converted value is padded on the right with 127blanks, rather than on the left with blanks or zeros. A '-' overrides a &'0' 128if both are given. 129 130## (space) 131 132(a space: ' ') A blank should be left before a positive number (or empty 133string) produced by a signed conversion. 134 135## + 136 137A sign (+ or -) should always be placed before a number produced by a signed 138conversion. By default, a sign is used only for negative numbers. A '+' 139overrides a space if both are used. 140 141# Field width 142 143An optional decimal digit string (with nonzero first digit) specifying a 144minimum field width. If the converted value has fewer characters than the 145field width, it gets padded with spaces on the left (or right, if the 146left-adjustment flag has been given). Instead of a decimal digit string one 147may write "*" or "*m$" (for some decimal integer m) to specify that the field 148width is given in the next argument, or in the *m-th* argument, 149respectively, which must be of type int. A negative field width is taken as 150a '-' flag followed by a positive field width. In no case does a nonexistent 151or small field width cause truncation of a field; if the result of a 152conversion is wider than the field width, the field is expanded to contain the 153conversion result. 154 155# Precision 156 157An optional precision in the form of a period ('.') followed by an optional 158decimal digit string. Instead of a decimal digit string one may write "*" or 159"*m$" (for some decimal integer m) to specify that the precision is given in 160the next argument, or in the *m-th* argument, respectively, which must be of 161type int. If the precision is given as just '.', the precision is taken to be 162zero. A negative precision is taken as if the precision were omitted. This 163gives the minimum number of digits to appear for **d**, **i**, **o**, 164**u**, **x**, and **X** conversions, the number of digits to appear 165after the radix character for **a**, **A**, **e**, **E**, **f**, and 166**F** conversions, the maximum number of significant digits for **g** and 167**G** conversions, or the maximum number of characters to be printed from a 168string for **s** and **S** conversions. 169 170# Length modifier 171 172## h 173 174A following integer conversion corresponds to a *short* or *unsigned short* 175argument. 176 177## l 178 179(ell) A following integer conversion corresponds to a *long* or 180*unsigned long* argument, or a following n conversion corresponds to a 181pointer to a long argument 182 183## ll 184 185(ell-ell). A following integer conversion corresponds to a *long long* or 186*unsigned long long* argument, or a following n conversion corresponds to 187a pointer to a long long argument. 188 189## q 190 191A synonym for **ll**. 192 193## L 194 195A following a, A, e, E, f, F, g, or G conversion corresponds to a long double 196argument. 197 198## z 199 200A following integer conversion corresponds to a *size_t* or *ssize_t* 201argument. 202 203# Conversion specifiers 204 205A character that specifies the type of conversion to be applied. The 206conversion specifiers and their meanings are: 207 208## d, i 209 210The int argument is converted to signed decimal notation. The precision, if 211any, gives the minimum number of digits that must appear; if the converted 212value requires fewer digits, it is padded on the left with zeros. The default 213precision is 1. When 0 is printed with an explicit precision 0, the output is 214empty. 215 216## o, u, x, X 217 218The unsigned int argument is converted to unsigned octal (o), unsigned decimal 219(u), or unsigned hexadecimal (**x** and **X**) notation. The letters 220*abcdef* are used for **x** conversions; the letters *ABCDEF* are 221used for **X** conversions. The precision, if any, gives the minimum number 222of digits that must appear; if the converted value requires fewer digits, it 223is padded on the left with zeros. The default precision is 1. When 0 is 224printed with an explicit precision 0, the output is empty. 225 226## e, E 227 228The double argument is rounded and output in the style **"[-]d.ddde±dd"** 229 230## f, F 231 232The double argument is rounded and output to decimal notation in the style 233**"[-]ddd.ddd"**. 234 235## g, G 236 237The double argument is converted in style f or e. 238 239## c 240 241The int argument is converted to an unsigned char, and the resulting character 242is written. 243 244## s 245 246The *const char ** argument is expected to be a pointer to an array of 247character type (pointer to a string). Characters from the array are written up 248to (but not including) a terminating null byte. If a precision is specified, 249no more than the number specified are written. If a precision is given, no 250null byte need be present; if the precision is not specified, or is greater 251than the size of the array, the array must contain a terminating null byte. 252 253## p 254 255The *void ** pointer argument is printed in hexadecimal. 256 257## n 258 259The number of characters written so far is stored into the integer pointed to 260by the corresponding argument. 261 262## % 263 264A '%' symbol is written. No argument is converted. 265 266# EXAMPLE 267 268~~~c 269const char *name = "John"; 270 271int main(void) 272{ 273 curl_mprintf("My name is %s\n", name); 274 curl_mprintf("Pi is almost %f\n", (double)25.0/8); 275} 276~~~ 277 278# AVAILABILITY 279 280These functions might be removed from the public libcurl API in the future. Do 281not use them in new programs or projects. 282 283# RETURN VALUE 284 285The **curl_maprintf** and **curl_mvaprintf** functions return a pointer to 286a newly allocated string, or NULL if it failed. 287 288All other functions return the number of characters actually printed 289(excluding the null byte used to end output to strings). Note that this 290sometimes differ from how the POSIX versions of these functions work. 291